Known three-dimensional image display devices include a three-dimensional image display device having a mirror assembly including a plurality of half mirrors disposed in a two-dimensional image display device. For example, Patent Documents 1, 2 and 5 disclose three-dimensional image display devices which produce three-dimensional images by simultaneously displaying a virtual image produced by half mirrors from an image displayed on a two-dimensional image display device on a plurality of display surfaces located in different positions in the depth direction when seen from the viewer. For example, the three-dimensional display device described in Patent Document 1 is suggested by the inventor of the present invention. This three-dimensional display device is formed by a plurality of half mirrors so that their heights decrease as they go further in the depth direction, and the range where an image region can be generated and visually recognized is expanded.
The thus-created three-dimensional image by disposing a plurality of half mirrors in the two dimensional image device and overlapping two-dimensional virtual images resembles settings used on the stage of a theatrical performance, and does not require special eye glasses. In terms of physiological factors of stereopsis, the device involves using all factors used to see normal stereopsis such as convergence, focusing, binocular parallax and motion parallax, and therefore the device causes no eye strain as experienced with a three-dimensional image device seen only with some of the factors such as binocular parallax and convergence.
Recently, as described in Patent Documents 3 and 4, providing portable terminals having display devices such as cellular phones and portable game devices with two-dimensional display and three-dimensional display functions has been suggested. That is, the technique described in Patent Document 3 includes a mechanism which invertibly retains a display device having a three-dimensional display screen by the lenticular method on cellular phones and the like. Moreover, in the technique described in Patent Document 4, an image is projected on a three-dimensional display component including built-in half mirrors, concave mirrors and other components, and displayed as a virtual stereoscopic image like it is floating in the space via a three-dimensional image display window of a cellular phone.